Particulate matter is the sum of all solid and liquid particles suspended in air, many of which are hazardous. This complex mixture contains for instance dust, pollen, soot, smoke, and liquid droplets. Particulate Matter (PM) is a major air pollutant in the Nigeria atmospheric environment. This study has reviewed PM pollution in all the geopolitical zones in Nigeria.

Urban air quality in major Nigeria's cities has suffered PM pollution from diverse sources. For instance, it was reported that TSP concentration range of 1,033 - 40,000 µg/m3 in Lagos (the industrial capital of Nigeria). There is a PM10 concentration range of 118.3 µg/m3 in Abuja in comparison to 132.0 µg/m3 in Maiduguri . There are two major contributing factors to PM in Nigeria namely Industrialisation and Harmattan.

Industrialisation is the period of social and economic change that transforms a human group from an agrarian society into an industrial one, involving the extensive re-organisation of an economy for the purpose of manufacturing. A study at a steel and iron industry in Lagos for PM10 and PM2.5 revealed concentration ranges of 86 - 8765 µg/m3 and 10 - 462 µg/m3, respectively. The unusually high concentrations of these PM size fractions may be harmful to the public, especially the residents living around the vicinity of the steelworks industry. Recently, a PM sampling at some selected sites in Lagos results (12-hour mean values) revealed concentrations of 27 and 69 µg/m3 for PM2.5 and PM10 respectively.  The high PM values measured at these cities may be traced directly to urbanization and population growth. Abuja (the capital city of Nigeria) recorded the lowest PM10 and PM2.5 concentrations. The Efe study has revealed the highest PM10 concentration in Maiduguri while the work of Obioh et al. in contrast, has showed Aba as the most polluted city in Nigeria. Emission sources like vehicular and industrial emissions might be responsible for high PM levels in Aba.  

Harmattan is another contributor to PM mass concentrations in every part of Nigeria, but mostly pronounced in the northern part of the country. Harmattan is a ground level stream of dry desert air from the African continental trade wind system that sweeps from a consistent northeast direction to the south during the boreal winter. During the Harmattan period, as high as 400-1200 kg/ha dust particles are deposited in the northern part of Nigeria compared to 100-400 kg/ha in the southern part of the nation. The lowest concentrations of PM10 were measured in July and September, the two peaks of rainfall in Nigeria. This could have been responsible for the low PM values documented at these months. Nevertheless, PM concentrations were high throughout the year. The lowest concentration of 130 µg/m3 reported in July and September was still higher than the reported values of PM10 and PM2.5 in European countries. 

The dry season showed the greatest peak of particle pollution in Nigeria. The monthly study of PM revealed January as the highest peak of PM pollution in Nigeria because of prevalence of Harmattan dust during this period. PM10 concentrations have been measured at a higher concentration at urban sites (>140 µg/m3) than the rural sites (> 50 µg/m3). Studies involving PM measurement at both urban and rural settings have been scarcely reported in published literature in Nigeria. 

Sources

www.greenfacts.org

www.cest2015.gnest.org/papers /cest2015_00342_poster_paper.pdf